//VGC_sample_code
#include iostream
#include <unordered_map>
#include vector
#include cstdint
#include functional
#include string
// VIRTUAL GARBAGE COLLECTOR (VGC) STATE DEFINITIONS:-
/**
* VGC State Machine - 3-bit encoding for object lifecycle management
*
* Each state represents a distinct phase in the object’s lifecycle,
* guiding the collector’s decisions about memory management.
*/
enum class VGC_State : uint8_t {
IDLE = 0b000, // Object is sleeping, waiting for activation
ACTIVE = 0b001, // Object is in active use, keep alive
PROMOTE = 0b010, // Candidate for moving to a higher-priority zone
DEMOTE = 0b011, // Candidate for moving to a lower-priority zone
PERSIST = 0b100, // Long-lived object, maintain regardless of zone
DEFERRED = 0b101, // Collection deferred to next cycle
MARKED = 0b110, // Flagged for potential deletion
EXPIRED = 0b111 // Ready for immediate reclamation
};
/**
* Memory Zone Classification
* Objects are assigned to zones based on their expected lifetime
* and access patterns, enabling differentiated collection strategies.
*/
enum class MemoryZone : uint8_t {
RED = 0b001, // Short-lived, high-turnover objects
GREEN = 0b010, // Medium-lived, regular objects
BLUE = 0b100 // Long-lived, persistent objects
};
/**
* Represents an object tracked by the VGC system
* Each object carries metadata that informs the collector’s decisions,
* balancing immediate needs with long-term memory health.
*/
struct VGC_Object {
uint32_t id; // Unique identifier for the object
uint8_t zone_mask; // Memory zone assignment (R/G/B mask)
uint8_t state; // Current lifecycle state (3-bit encoding)
// Helper function for human-readable state display
std::string state_name() const {
switch (static_cast<VGC_State>(state)) {
case VGC_State::IDLE: return "IDLE";
case VGC_State::ACTIVE: return "ACTIVE";
case VGC_State::PROMOTE: return "PROMOTE";
case VGC_State::DEMOTE: return "DEMOTE";
case VGC_State::PERSIST: return "PERSIST";
case VGC_State::DEFERRED: return "DEFERRED";
case VGC_State::MARKED: return "MARKED";
case VGC_State::EXPIRED: return "EXPIRED";
default: return "UNKNOWN";
}
}
// Helper function for human-readable zone display
std::string zone_name() const {
switch (zone_mask) {
case static_cast<uint8_t>(MemoryZone::RED): return "RED";
case static_cast<uint8_t>(MemoryZone::GREEN): return "GREEN";
case static_cast<uint8_t>(MemoryZone::BLUE): return "BLUE";
default: return "MIXED_ZONE";
}
}
};
/**
* Virtual Garbage Collector Manager
* Implements a zone-aware collection strategy using a logic gate approach
* to determine object liveness based on state, zone, and pending operations.
*/
class VGC_Manager {
private:
// Storage for managed objects, keyed by object ID
std::unordered_map<uint32_t, VGC_Object> heap;
// Collection of callbacks to execute before sweeping
std::vector<std::function<void()>> pre_sweep_callbacks;
// Collection of callbacks to execute after sweeping
std::vector<std::function<void(size_t)>> post_sweep_callbacks;
public:
/\*\*
\* Allocates a new object into the managed heap
\* @param id Unique identifier for the object
\* @param zone Memory zone assignment (Red/Green/Blue)
\* @param initial_state Starting lifecycle state (defaults to ACTIVE)
\*/
void allocate(uint32_t id, MemoryZone zone, VGC_State initial_state = VGC_State::ACTIVE) {
if (heap.count(id)) {
std::cerr << "Warning: Object " << id << " already exists. Overwriting.\\n";
}
VGC_Object new_object = {
id,
static_cast<uint8_t>(zone),
static_cast<uint8_t>(initial_state)
};
heap\[id\] = new_object;
std::cout << "Allocated object " << id
<< " in " << new_object.zone_name()
<< " zone with state: " << new_object.state_name() << "\\n";
}
/\*\*
\* Core liveness evaluation logic
\* Implements the VGC decision equation: O = (S & Z) | (S & P)
\* Where: S = current state, Z = zone mask, P = pending operations mask
\* This forms the heart of the collector's decision-making process,
\* determining whether an object should survive the current collection cycle.
\*/
bool evaluate_liveness(const VGC_Object& obj, uint8_t pending_mask = 0) const {
uint8_t current_state = obj.state;
uint8_t zone_mask = obj.zone_mask;
uint8_t pending_ops = pending_mask;
// Special case: EXPIRED objects must always be collected
if (static_cast<VGC_State>(current_state) == VGC_State::EXPIRED) {
return false;
}
// Special case: PERSIST objects survive regardless of other factors
if (static_cast<VGC_State>(current_state) == VGC_State::PERSIST) {
return true;
}
// Apply the core VGC liveness equation
uint8_t liveness_score = (current_state & zone_mask) | (current_state & pending_ops);
// Objects with any liveness indication survive
return liveness_score > 0 ||
static_cast<VGC_State>(current_state) == VGC_State::ACTIVE;
}
/\*\*
\* Register a callback to execute before each sweep operation
\*/
void register_pre_sweep_callback(std::function<void()> callback) {
pre_sweep_callbacks.push_back(callback);
}
/\*\*
\* Register a callback to execute after each sweep operation
\* Callback receives the number of objects reclaimed
\*/
void register_post_sweep_callback(std::function<void(size_t)> callback) {
post_sweep_callbacks.push_back(callback);
}
/\*\*
\* Perform a garbage collection sweep
\* Identifies unreachable objects using the liveness evaluation logic
\* and reclaims their memory, maintaining heap health.
\*/
void sweep(uint8_t pending_mask = 0) {
std::cout << "\\n--- Initiating VGC Collection Cycle ---\\n";
// Execute pre-sweep hooks (e.g., pause application threads)
for (const auto& callback : pre_sweep_callbacks) {
callback();
}
// Identify objects that are no longer alive
std::vector<uint32_t> objects_to_reclaim;
for (const auto& \[id, obj\] : heap) {
if (!evaluate_liveness(obj, pending_mask)) {
objects_to_reclaim.push_back(id);
}
}
// Report and reclaim identified objects
if (!objects_to_reclaim.empty()) {
std::cout << "Reclaiming " << objects_to_reclaim.size()
<< " object(s):\\n";
for (uint32_t id : objects_to_reclaim) {
const auto& obj = heap\[id\];
std::cout << " • Object " << id
<< " (Zone: " << obj.zone_name()
<< ", State: " << obj.state_name() << ")\\n";
heap.erase(id);
}
} else {
std::cout << "No objects eligible for reclamation.\\n";
}
// Execute post-sweep hooks (e.g., resume application threads, update stats)
for (const auto& callback : post_sweep_callbacks) {
callback(objects_to_reclaim.size());
}
std::cout << "--- Collection Cycle Complete ---\\n";
}
/\*\*
\* Transition an object to a new lifecycle state
\* @param id Object identifier
\* @param new_state Target state for the transition
\*/
void transition_state(uint32_t id, VGC_State new_state) {
auto it = heap.find(id);
if (it != heap.end()) {
VGC_State old_state = static_cast<VGC_State>(it->second.state);
it->second.state = static_cast<uint8_t>(new_state);
std::cout << "Object " << id
<< " transitioned: "
<< it->second.state_name()
<< " (was: ";
// Create temporary object to get old state name
VGC_Object temp = it->second;
temp.state = static_cast<uint8_t>(old_state);
std::cout << temp.state_name() << ")\\n";
} else {
std::cerr << "Error: Cannot transition state. Object "
<< id << " not found.\\n";
}
}
/\*\*
\* Display current heap status in a human-readable format
\*/
void display_status() const {
std::cout << "\\n=== VGC Heap Status ===\\n";
std::cout << "Total Managed Objects: " << heap.size() << "\\n";
if (heap.empty()) {
std::cout << "Heap is empty.\\n";
return;
}
// Display summary by zone
std::cout << "\\nZone Distribution:\\n";
size_t red_count = 0, green_count = 0, blue_count = 0;
for (const auto& \[id, obj\] : heap) {
if (obj.zone_mask == static_cast<uint8_t>(MemoryZone::RED)) red_count++;
else if (obj.zone_mask == static_cast<uint8_t>(MemoryZone::GREEN)) green_count++;
else if (obj.zone_mask == static_cast<uint8_t>(MemoryZone::BLUE)) blue_count++;
}
std::cout << " RED Zone (Short-lived): " << red_count << " objects\\n";
std::cout << " GREEN Zone (Medium-lived): " << green_count << " objects\\n";
std::cout << " BLUE Zone (Long-lived): " << blue_count << " objects\\n";
// Display detailed object listing
std::cout << "\\nDetailed Object List:\\n";
std::cout << "ID | Zone | State | Alive?\\n";
std::cout << "-------|--------|------------|--------\\n";
for (const auto& \[id, obj\] : heap) {
bool is_alive = evaluate_liveness(obj);
std::cout << std::setw(6) << id << " | "
<< std::setw(6) << obj.zone_name() << " | "
<< std::setw(10) << obj.state_name() << " | "
<< (is_alive ? "YES" : "NO") << "\\n";
}
std::cout << "======================================\\n";
}
/\*\*
\* Get the current number of managed objects
\*/
size_t object_count() const {
return heap.size();
}
};
// DEMONSTRATION OF THE VGC SYSTEM
int main() {
VGC_Manager collector;
// Register some callbacks to demonstrate extensibility
collector.register_pre_sweep_callback(\[\]() {
std::cout << "\[Pre-sweep\] Pausing application threads...\\n";
});
collector.register_post_sweep_callback(\[\](size_t reclaimed_count) {
std::cout << "\[Post-sweep\] Resuming application threads. "
<< reclaimed_count << " objects reclaimed.\\n";
});
std::cout << "=== Virtual Garbage Collector Demonstration ===\\n\\n";
// Phase 1: Object Allocation with Zone Assignment
std::cout << "Phase 1: Allocating Objects into Zones\\n";
collector.allocate(101, MemoryZone::GREEN, VGC_State::ACTIVE);
collector.allocate(102, MemoryZone::RED, VGC_State::MARKED);
collector.allocate(103, MemoryZone::BLUE, VGC_State::PERSIST);
collector.allocate(104, MemoryZone::GREEN, VGC_State::IDLE);
collector.allocate(105, MemoryZone::RED, VGC_State::ACTIVE);
collector.display_status();
// Phase 2: Simulating Application Behavior with State Transitions
std::cout << "\\n\\nPhase 2: Simulating Application Runtime Behavior\\n";
collector.transition_state(102, VGC_State::EXPIRED); // Marked -> Expired
collector.transition_state(104, VGC_State::ACTIVE); // Idle -> Active
collector.transition_state(105, VGC_State::DEMOTE); // Active -> Demote candidate
collector.display_status();
// Phase 3: Garbage Collection Sweep
std::cout << "\\n\\nPhase 3: Executing Garbage Collection\\n";
// First sweep with no pending operations
collector.sweep();
collector.display_status();
// Simulate pending operations (e.g., references from recently allocated objects)
std::cout << "\\n\\nPhase 4: Simulating Pending Operations\\n";
collector.allocate(106, MemoryZone::GREEN, VGC_State::ACTIVE);
collector.allocate(107, MemoryZone::RED, VGC_State::ACTIVE);
// Create a pending mask that might affect liveness decisions
uint8_t pending_operations_mask = 0b011; // Example pending operations
std::cout << "\\nExecuting sweep with pending operations mask: "
<< static_cast<int>(pending_operations_mask) << "\\n";
collector.sweep(pending_operations_mask);
collector.display_status();
std::cout << "\\n=== Demonstration Complete ===\\n";
std::cout << "Final heap contains " << collector.object_count()
<< " managed objects.\\n";
return 0;
}
